Axial-piston machine

ABSTRACT

An axial-piston machine in which the cylinder drum is rotatably entrained with a shaft extending through this drum while means enables relative axial displacement of shaft and drum. A stack of BELLEVILLE washers is seated against the lower shaft bearing and acts via a plurality of angularly spaced pins on a swivel cap which, in turn, engages a disk holding the piston shoes against an inclined control surface surrounding the axis of the shaft. The cylinder drum is applied by a further spring against a fluiddistribution surface, this spring being seated at least in part against a perforated disk through which the force-transmitting pins or rods extend.

United States Patent [151 3,678,804

Heyl [4-51 July 25, 1972 [54] AXIAL-PISTON MACHINE 3,292,553 12/1966 Hann ..91/507 [72] inventor: Walter Heyl, Klein-Umstadt, Germany 2:532?

[73] Assignee: Linde Aktiengesellschaft, Wiesbaden, Ger- 3,405,646 10/1968 T a 91/499 ma 3,522,759 8/1970 Martin ..91/507 [22] Filed: 1970 Primary Examiner-William L. Freeh Appl. No.: 68,254

Attorney-Karl F. Ross 57 ABSTRACT An axial-piston machine in which the cylinder drum is rotatably entrained with a shaft extending through this drum while means enables relative axial displacement of shaft and drum. A stack of BELLEVILLE washers is seated against the lower shaft bearing and acts via a plurality of angularly spaced pins on a swivel cap which, in turn, engages a disk holding the piston shoes against an inclined control surface surrounding the axis of the shaft. The cylinder drum is applied by a further spring against a fluid-distribution surface, this spring being seated at least in part against a perforated disk through which the force-transmitting pins or rods extend.

9 Claims, 4 Drawing, Figures PKTE'NTEMLZ IW: 3.678.804

SHEEI 1 0F 2 l0 INVENTOR.

loo WALTER HEYL BY 'T fl ATTORNEY 1 AXIAL-PISTON MACHINE FIELD OF THE INVENTION My present invention relates to axial-piston machines and, more particularly, to an axial-piston machine having improved mounting of the cylinder drum.

BACKGROUND OF THE INVENTION The term axial-piston machine is used generally in the art of fluid mechanics to indicate broadly a hydraulic pump or hydraulic motor having a plurality of pistons extending along an axis of rotation for displacing a hydraulic fluid or for displacement thereby. For the most part, an axial-piston pump can be driven to displace the fluid or, when connected as a motor to a source of hydraulic pressure, will rotate the drum to produce a torque Output. Hence the expression is intended to indicate machines of the configuration described below which may be used both as a pump and as a motor or may be designed so that they can only operate either as a pump or as a motor.

Axial-piston machines of this type comprise a fluid-distribution surface, generally extending transversely to the axis of rotation of the drum and provided with arcuate or kidneyshaped fluid-distribution ports. The cylinder drum or barrel may be rotatably mounted upon a shah extending perpendicular to this surface and urged against the latter while being provided with a plurality of cylinder bores in angularly equispaced relationship about the shaft. The bores open away from the surface, but may have passages communicating with the fluid-distribution passages at the latter surface whereby hydraulic fluid dispensed from the cylinder bores is collected and transmitted to the discharge port of a hydraulic pump, in an alternate mode or hydraulic fluid is induced to flow into the cylinder bores from an intake port of such pump, or hydraulic fluid is forced into the cylinder bores through the inlet side of a hydraulic motor; also, hydraulic fluid can be led to a reservoir or other low pressure component through the discharge side of such motor.

Each of the cylinder bores slidably receives a piston or plunger which may have an end extending beyond the mouth of the cylinder bore and bearing upon a control plate or surface lying generally at an incline to the axis of rotation of the drum. As each of the cylinder bores and the pistons entrained thereby orbit this axis, therefore, depending upon the relative spacing of the control surface portion engaged by the piston from the fluid-distribution surface, the cylinder chambers behind each piston will be contacted or expanded, thereby giving rise to compression in the case of a pump or the generation of a torque in the case of a motor.

Numerous means have been provided in axial-piston machines of this type to retain the drum against the fluid-distribution surface, such means including differential-piston arrangements which rely upon the pressure at the high pressure side of the machine to hold the cylinder drum against the fluid-distribution surface, springs surrounding the shaft and bearing upon the drum, and the like. In addition, thrust bearings may be provided between such means and the rotating drum, while radial bearings can support the latter upon the stationary shaft on which the drum may be mounted.

Furthermore, mention may be made of systems, with which the present invention is primarily concerned, in which the drum is fixedly aligned with the shaft, such systems being provided in many cases. In these systems, the control surface may be stationary and the individual pistons may be provided with shoes or the like enabling them to slide along the control surface as the drum is rotated. Spring means or the like may be used to ensure the maintenance of a pressure of the shoe and piston against the guide surface and the shoe may be coupled with the piston via a ball joint or other universal joint means. The invention is equally applicable to arrangements in which the pistons bear directly against the guide surface (without shoes).

It has also been proposed to apply the spring means by a disk engaging the surface of the shoes remote from the control surface and thereby prevent pressure buildup beneath the shoes from withdrawing them from contact with the control surface and, similarly, preventing vibration or inertial effects from permitting the shoes to leave sliding contact with the control surface. All of this, however, has required complex structures in the past, has given rise to the possibility of seizing or locking of the relatively movable surfaces as a consequence of the high pressures involved and, especially, because of thermal expansion as a result of heat generated in the machine. Supply of fluid under pressure between the slidingly engageable surfaces of the shoe and the inclined control member, moreover, to prevent undue pressure of the shoe against the control member and provide a fluid film to reduce friction, has further complicated the problem.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invenu'on to provide an improved axial-piston machine of the general class described wherein the aforementioned disadvantages are avoided.

Another object of the invention is to provide an axial-piston machine having a cylinder drum rotatably entrained with a shaft and means for retaining a plurality of glide shoes against an inclined control surface without detrimentally increasing the force with which the cylinder drum bears upon its fluiddistribution surface.

Still another object of my invention is to provide an axialpiston machine, an axial-piston pump or motor, having simplified means for retaining the piston shoes against a control surface inclined to the axis of rotation of the piston drum or barrel.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter, are attained in an axial-piston machine having a housing formed with the usual fluid-distribution surface or plate, in which a shah is journaled for rotation about an axis perpendicular to the fluid-distribution surface and rotatably entrains a cylinder drum whereby relative axial movement of the cylinder drum and the shaft is permitted.

According to an essential feature of this invention, a first spring means is provided around this shaft in conjunction with a spring seat in the form of a perforated disk to bias the shaft and the drum in opposite axial directions so as to resiliently retain the drum against the fluid-distribution surface, while second spring means around the shaftcooperates with a plurality of rods or pins extending axially through the perfora tions disk to bear upon a ball or swivel arrangement axially shiftable relative to the drum and retaining a disk against the shoes of the pistons which are axially displaceable in this drum. The second spring means axially acts upon a bearing rotatably supporting the shaft within the housing.

According to a further feature of this invention, the first spring means is a helical coil spring directly or indirectly seated against the drum along an inner surface thereof surrounding the shaft with clearance to accommodate both of the spring means and the force-transmitfing members associated therewith. The second spring means may be constituted by a stack of dished-disk or Belleville washers bearing axially upon a sleeve surrounding the shaft and constituting a forced transmitting member which acts upon the array of pins. The perforated plate can be mounted directly upon the shaft, although best results are obtained when the perforated plate, in turn, acts upon a sleeve which is seated against a shoulder of the shaft.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of my present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is an axial cross-sectional view of an axial-piston machine according to the present invention;

FIG. 2 is a cross-sectional view taken along line II-Il thereof; and

FIGS. 3 and 4 are detailed views illustrating modifications of the invention.

SPECIFIC DESCRIPTION In the drawing I show an axial-piston machine having a drive shaft 1 connected by splines 2 to the cylinder drum 3 which, consequently, is rotatably entrained with the shaft 1 or rotatably entrains the latter, but is free to move axially relative to this shaft. The cylinder drum 3 is provided with a plurality of angularly equispaced cylinder bores 4 with axes parallel to the axis of the shaft 1 and of the cylinder drum, each of the cylinder bores 4 receiving an axially shiftable piston 5. Each of the pistons is formed with a free end adapted to project beyond the mouth of the cylinder bore 4 and provided with a ball-shaped head 6 forming a swivel joint with a glide shoe 7 which has a generally spheroidal seat accommodating the ballshaped head and hugging the latter. The cylindrical shoe 7 has an outwardly extending flange 14 which bears with a diskshaped portion 8 against the inclined surface of an annular body 9 serving as the control surface of the machine. The body 9 in the machine illustrated in FIGS. 1 and 2 is shown to be fixedly positioned, although it will be understood that such bodies may be mounted for angular displacement about an axis perpendicular to the axis of the shaft 1 to adjust the angle with which the control-surface plane, along which the disks 8 sweep, intersects the axis of the drum.

The control plate 9 is mounted in a housing 10 within which the drum is rotatable. I

Each of the glide shoes 7 is provided with a recess 11 opening toward the inclined face of member 9 and provided at the end of a longitudinally extended bore 12' which opens into the spheroidal seat accommodating the ball 6. A bore 12 extending axially through each piston 5, likewise opens into spheroidal seat and communicates with the chamber within cylinder 4 beyond each piston so that the recess 1 1 is continuously under the fluid pressure of the associated cylinder 4.

The shoes 7 are held in place against the control body 9 by a pressure plate 13 in the form of a perforated disk having openings 15 accommodating the shoes 7 with play, but bearing upon the flanges 14 of each shoe. A central, generally spheroidal recess 13' in the hub of the disk 13 is fitted over a ball-shaped member 16 which is rotatably entrained with the drum by being splined at 2 to the shaft 1 while the boss 3a is likewise keyed to the shaft at splines 2. Hence, the plate 13 is free to swivel about an axis perpendicular to the plane of the paper in FIG. 1 and represented at A therein, the axis A being perpendicular to the axis of rotation of the drum represented at B.

At one end, the shaft 1 is journaled via a tapered roller bearing assembly 17 for rotation in the housing 10. The latter includes a base plate 10 which is bolted to the cylindrical housing portion 10" by bolts 10a and is centered with respect to the housing by pins 10b. The bearings 17 includes an inner ring or race carried by a stub la of the shaft 1 and an outer race 17a seated in a recess 100 formed axially in the plate 10. Tapered rollers 17b form a ring between the recess in accordance with conventional practice. A bearing 18 is provided at the upper end of the shaft and is dimensioned to withstand greater radial stress than the bearing 17 since the shaft 1 may be provided at its end lb with a gear, pulley or the like or transmission of torque to a load or for driving the machine. The bearing 18, in turn, includes an outer race 18a seated in an axially extending recess 10d at the upper end of housing 10, an inner race 18b axially retaining the shaft 1 via a shoulder 1c of the latter and surrounding the bores 1d thereof, and a crown of tapered rollers 180. A retaining ring We holds the assembly in place. The plate 10' is further provided with a passage 21 forming part of a lubricantcirculating path and opening into the recess 100 to assure passage of lubricant through the bearing. The lubricant can, of course, be part of the hydraulic fluid used in the axial-piston machine. A port 22 is provided for the leakage oil.

To apply the shoes 7 to the control surface of the body 9, I provide a stack of dished-spring disks 19 (i.e. Belleville washers) at the lower end of the stack being seated axially against the inner race 20 of the baring 17. At its upper end, the stack 19 of Belleville washers bears against an abutment ring 22 axially shiftable along the exterior of a guide sleeve 22a surrounding a step 1d of the shafi l. The ring 22 bears axially upon the lower end of a force-transmission sleeve 23 surrounding the large-diameter step 1c of the shaft and bearing, in turn, upon a ring 24 against which a plurality of pins 25 rest. The pins 25 extend parallel to the axis 3 and are angularly equispaced about the drum 3. To this end, the drum 3 is formed with a boss 3a of cylindrical outer periphery upon which the generally spheroidal body 16 is axially shifiable and carrying the splines of the drum which interfit with the splines 2 of the shaft 1. This boss is further formed with a plurality of axially extending, angularly equispaced small-diameter bores 3b slidably accommodating the pins 25 to permit the latter to shift axially relative to the drum. The pins, in turn, bear axially against an inner surface 26 of the body 16 which lies generally transversely to the axis B of the shaft. Consequently, the pins 25 bias to body 16 upwardly while this member 16 urges the disk 13 upwardly to retain the shoes 7 against the member 9 without exerting any counter pressure upon the drum in the direction of the fluid-distribution chamber 27.

To develop pressure for retaining the drum 3 against the fluiddistributing surface 27, which is centered on the aperture plate 10b of the housing 10 by pins 270, I provide a helical coil spring 28 which coaxially surrounds the sleeve 23 and the shaft 1. At its lower end the spring 28 bears upon a seating ring 29 which is, in turn, in abutting relationship with a spring ring 30 recessed in the inner wall 30 of the drum 3. The upper end of the spring 28 bears axially upon a spring seat 31 having a cylindrical sleeve-portion 32 lying outwardly of and clearing the ring 24. The cylindrical portion 32 bears axially upon a disk 33 which is formed with perforations through which the rods 25 extend with play. The perforated disk 33, in turn, acts upon a sleeve 35 coaxially surrounding step 1e of the shaft and bearing upon a shoulder 1f thereof. The shoulder If, consequently, is rigid with the shoulder 10 which is seated against the inner race 18b of the bearing 18. Since the shaft 1 and the drum 3 are engaged with limited freedom of relative axial movement, the bearing 18 is held under the prestress of spring 28 whereas the bearing 17 is held under the prestress of spring 19 which also serves to bias the shoes 7 against the control body 9. The shoes 7 are formed along their disk-shaped surfaces 8 with annular grooves 36 confronting the surface of member 9 and forming a labyrinth seal around the recess 11. The working fluid is removed via port 37 and supplied to the machine by a further port not shown. The underside of the drum 3 may be coated with a layer 3d of bronze to reduce friction.

As shown in FIG. 3, the perforated plate 133 need not transfer force indicated to the shaft as illustrated in FIG. 1 via the sleeve 35, but may be anchored directly to the shaft. Preferably, this may be done by screw-threading the shaft 101 and the disk 133 complementarily. The rods 125 pass through the perforations 134 of the disk in the manner previously described. FIG. 4 shows a modification of the second spring means according to the invention, the Belleville washers 19, which may be coated to prevent corrosion, being replaced by a sleeve 119 of an elastomeric material. This second spring means may, moreover, be simply a block of rubber provided with an opening to receive the shaft 101. The sleeve 119 is seated against the inner bearing race 120 of bearing 117 while resting against the ring 122 which, in turn, acts upon the forcetransmitting sleeve as illustrated at 23 in FIG. 1.

The improvement described and illustrated is believed to admit of many modifications within the ability or persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

Iclaim:

1. An axial piston machine comprising:

a housing having a fluid-distribution surface;

a cylinder drum received in said housing for rotation about an axis generally transverse to said surface and provided with a plurality of angularly spaced cylinders each communicating with said surface;

a shaft keyed to said cylinder drum for rotatable entrainment therewith while permitting relative axial displacement of said drum and said shaft;

an inclined guide body in said housing surrounding said shaft, said drum being provided with respective pistons each axially displaceable in a respective one of said cylinders and having a shoe slidably engaging said body;

pressure means axially shiftable relative to said shaft for retaining said shoes against said body;

first spring means bearing in opposite axial directions upon said drum and said shaft for urging said drum against said surface, said first spring means including a perforated disk acting upon said shaft; and

second spring means surrounding said shaft and including a plurality of rods extending through perforations in said disk and acting upon said pressure means for urging same toward said body, said cylinder drum being provided with an annular shoulder surrounding said shaft at an intermediate location along the length of said cylinder drum, said first spring means including a first spring coaxially surrounding said shaft and bearing axially upon said disk and said shoulder, said second spring means including:

a second spring coaxially surrounding said shaft and disposed between said first spring and said surface,

a sleeve surrounding said shaft and coaxial with said first spring and with said shaft while being axially shiftable and seated against said second spring, and

a ring axially entrained by said sleeve and bearing upon said rods.

2. The machine defined in claim 1 wherein said first spring means includes a coil spring bearing at one end against said perforated disk and a spring seat anchored to said drum around said shaft and engaging the other end of said coil spring.

3. The machine defined in claim 11 wherein said second spring is a stack of Belleville washers.

4. The machine defined in claim 1 wherein said second spring is seated at its side opposite said sleeve against said shaft.

5. The machine defined in claim 1, further comprising first bearing means at one end of said shaft and second bearing means at the other end of said shaft for rotatably journaling shaft within said housing, said first spring means generating a force transmitted by said shaft axially to said first bearing means and said second spring means generated a force transmitted axially to said second bearing means.

6. The machine defined in claim 5 wherein said first spring means includes force-transmitting means between said perforated disk and said shaft.

7. The machine defined in claim 6 wherein the force-transmitting means of said first spring means includes a sleeve coaxially surrounding said shaft.

8. The machine defined in claim 6 wherein said perforated disk is threaded onto said shaft.

9. The machine defined in claim 11, further comprising a first tapered-roller hearing at an end of said shaft remote from said surface and including an outer race anchored in said housing, an inner race axially abutting said shaft and an array of tapered rollers between said races; second bearing means at an end of said shaft proximal to said surface and including an inner race anchored to said shaft, an array of tapered rollers surrounding said inner race and an outer race received in said housing, said second spring means including a stack of Belleville washers seated against inner race of said second bearing means and coaxially surrounding said shaft, an abutment ring bearing against said stack, a first force-transrnitting sleeve engaging said ring and coaxially surrounding said shaft, and a further ring engaging said sleeve and bearing upon said rods; said first spring means including a seat formed on said drum around said sleeve, a helical coil spring bearing upon said seat on said drum at one end of said coil spring, the other end of said coil spring bearing upon said perforated disk, and another sleeve coaxially surrounding said shaft and biased axially by said perforated disk and said coil spring in the direction of said first hearing means, said other sleeve engaging said shaft in the axial direction. 

1. An axial piston machine comprising: a housing having a fluid-distribution surface; a cylinder drum received in said housing for rotation about an axis generally transverse to said surface and provided with a plurality of angularly spaced cylinders each communicating with said surface; a shaft keyed to said cylinder drum for rotatable entrainment therewith while permitting relative axial displacement of said drum and said shaft; an inclined guide body in said housing surrounding said shaft, said drum being provided with respective pistons each axially displaceable in a respective one of said cylinders and having a shoe slidably engaging said body; pressure means axially shiftable relative to said shaft for retaining said shoes against said body; first spring means bearing in opposite axial directions upon said drum and said shaft for urging said drum against said surface, said first spring means including a perforated disk acting upon said shaft; and second spring means surrounding said shaft and including a plurality of rods extending through perforations in said disk and acting upon said pressure means for urging same toward said body, said cylinder drum being provided with an annular shoulder surrounding said shaft at an intermediate location along the length of said cylinder drum, said first spring means including a first spring coaxially surrounding said shaft and bearing axially upon said disk and said shoulder, said second spring means including: a second spring coaxially surrounding said shaft and disposed between said first spring and said surface, a sleeve surrounding said shaft and coaxial with said first spring and with said shaft while being axially shiftable and seated against said second spring, and a ring axially entrained by said sleeve and bearing upon said rods.
 2. The machine defined in claim 1 wherein said first spring means includes a coil spring bearing at one end against said perforated disk and a spring seat anchored to said drum around saiD shaft and engaging the other end of said coil spring.
 3. The machine defined in claim 1 wherein said second spring is a stack of Belleville washers.
 4. The machine defined in claim 1 wherein said second spring is seated at its side opposite said sleeve against said shaft.
 5. The machine defined in claim 1, further comprising first bearing means at one end of said shaft and second bearing means at the other end of said shaft for rotatably journaling shaft within said housing, said first spring means generating a force transmitted by said shaft axially to said first bearing means and said second spring means generated a force transmitted axially to said second bearing means.
 6. The machine defined in claim 5 wherein said first spring means includes force-transmitting means between said perforated disk and said shaft.
 7. The machine defined in claim 6 wherein the force-transmitting means of said first spring means includes a sleeve coaxially surrounding said shaft.
 8. The machine defined in claim 6 wherein said perforated disk is threaded onto said shaft.
 9. The machine defined in claim 1, further comprising a first tapered-roller bearing at an end of said shaft remote from said surface and including an outer race anchored in said housing, an inner race axially abutting said shaft and an array of tapered rollers between said races; second bearing means at an end of said shaft proximal to said surface and including an inner race anchored to said shaft, an array of tapered rollers surrounding said inner race and an outer race received in said housing, said second spring means including a stack of Belleville washers seated against inner race of said second bearing means and coaxially surrounding said shaft, an abutment ring bearing against said stack, a first force-transmitting sleeve engaging said ring and coaxially surrounding said shaft, and a further ring engaging said sleeve and bearing upon said rods; said first spring means including a seat formed on said drum around said sleeve, a helical coil spring bearing upon said seat on said drum at one end of said coil spring, the other end of said coil spring bearing upon said perforated disk, and another sleeve coaxially surrounding said shaft and biased axially by said perforated disk and said coil spring in the direction of said first bearing means, said other sleeve engaging said shaft in the axial direction. 